Dying dogwood and serviceberries (partially)

(Question)

Hi my dogwood and serviceberries have some branches that seem dying. The top half of the dogwood seems completely dead. And a really long brand of the serviceberries is dark black with lots of spots on it. All those branches have not produced any leaves or flowers for at least a season or two. I wonder if this is an infection and if it would spread to the entire tree if I don’t do something about it.
Please advise what I should do to manage the situation? Thanks. I can’t upload more than photos here. but I would be happy to send it the email below if you’d like. let me know.
Cheers

(Answer)

Thanks so much for contacting Toronto Master Gardeners regarding the issues with your trees.

We have a couple of ideas on what may be going on:

On the darker black sections of the branches, does the black area seem to be mildewy like it can almost be scratched away? If that is the case, this may be sooty mold, which is a fungus. This excellent article by the University of California  http://ipm.ucanr.edu/PMG/PESTNOTES/pn74108.html provides a description of the problem and a management strategy, as well as an appendix on pests, specifically ants which may be central to the problem. If sooty mold is indeed the issue, this is a sign that further inspection is needed because more than likely there are insects that are the underlying cause of dying branches.

Here are a couple additional articles on sooty mold:

Sooty Mold

https://ag.umass.edu/landscape/fact-sheets/sooty-mold

For your Dogwood, we also think that a twig and branch canker caused by fungal pathogens (Botryosphaeria) could be the culprit. This can cause dieback. Here are some helpful articles that provide more information:

Given that the affected area is taking over a large portion of the trees, we’d recommend having a consultation with an arborist help to take the appropriate action and confirm the issues at hand. They would be able to help by containing the spread by both pruning affected branches and treating the issue of the insects.

We wish for you all the best in remedying this issue!